Field of the Invention
The present invention relates to a zoom lens and an image pickup apparatus including the same, and is suitable for image pickup optical systems used for image pickup apparatuses, such as a digital camera, a video camera, a TV camera, a monitoring camera, and a silver halide film camera.
Description of the Related Art
A zoom lens that has a wide imaging angle of view and a short total length, and is small in size as a whole and light in weight is demanded as an image pickup optical system used for an image pickup apparatus. Conventionally, a negative-lead type zoom lens where a lens unit having a negative refractive power is disposed closest to the object side has been known as a zoom lens that is small in size over the entire system and has a wide angle of view. Japanese Patent Application Laid-Open No. 2014-006275 discloses a two-unit zoom lens that includes, in order from an object side to an image side: a first lens unit having a negative refractive power; and a second lens unit having a positive refractive power, the zoom lens performing zooming by changing the interval between the lens units.
Japanese Patent Application Laid-Open No. 2007-78834 discloses a three-unit zoom lens and a four-unit zoom lens that include, in order from an object side to an image side: a first lens unit having a negative refractive power; a second lens unit having a positive refractive power; and at least one lens unit, the zoom lens performing zooming by changing the interval between adjacent lens units. Japanese Patent Application Laid-Open No. 2009-031358 discloses a four-unit zoom lens that includes, in order from an object side to an image side: a first lens unit having a negative refractive power; a second lens unit having a positive refractive power; a third lens unit having a negative refractive power; and a fourth lens unit having a positive refractive power, the zoom lens performing zooming by changing the interval between adjacent lens units.
In a negative-lead type zoom lens, a first lens unit disposed closest to the object side tends to be large and heavy in weight. At the first lens unit, the incident height of off-axial rays at a wide angle end is high. Consequently, the first lens unit causes strong various aberrations, such as the field curvature aberration, astigmatism and distortion. For achieving high optical characteristics of a negative-lead type zoom lens while facilitating reduction in size over the entire system and reduction in weight, it is important to set appropriately the lens configuration of the first lens unit.